The present invention relates to a linear guide apparatus, and more particularly relates to a sealing device for a linear guide apparatus which lubricant can be stably fed to the rolling elements over a long period of time.
Further, the present invention relates to a linear guide apparatus, and more particularly relates to a linear guide apparatus, to the lip portion of the sealing device of which lubricant can be automatically fed, so that the life of the sealing device can be prolonged.
A first conventional example will be described as follows. An example of the conventional linear guide apparatus, which is commonly used, is shown in FIG. 37. This conventional linear guide apparatus includes: a guide rail 1 extending in the axial direction, on the outer surface of which a rolling element rolling groove 3 is formed; and a slider 2 incorporated to the guide rail 1 in such a manner that the slider 2 strides the guide rail 1. The slider 2 is composed of a slider body 2A and end caps 2B attached to both ends of the slider body 2A. On inner side surfaces of both wing portions 4 of the slider body 2A, there are provided rolling element rolling grooves (not shown in the drawing) which are opposed to the rolling element rolling groove 3 formed on the guide rail 1. Also, in the slider body 2A, there are provided rolling element returning paths (not shown) which penetrate thick portions of the wing portions of the slider body 2A. On the other hands, the end caps 2B have curved paths (not shown) which communicate the rolling element rolling grooves of the slider body 2A with the rolling element returning paths formed in parallel to the rolling element rolling grooves. In this way, a circulation circuit of the rolling elements is formed by the rolling element rolling grooves, the rolling element returning paths and the curved paths formed on both sides. For example, a large number of rolling elements composed of steel balls are charged into the circulation circuit in which the rolling elements are circulated.
The slider 2 incorporated to the guide rail 1 is smoothly moved along the guide rail 1 when the rolling elements are rolling in both rolling element grooves which are opposed to each other. While the rolling elements are rolling in this way, they circulate endlessly in the rolling element circulation passages formed in the slider.
As a sealing device to seal an opening between the slider 2 and the guide rail 1 for the purpose of dust protection, as shown in FIG. 38, there are provided side seals 5 on both ends (end faces of the end caps 2B), and also there is provided an under seal 6 on the lower surface of the slider 2. Conventionally, these seals are made of rubber such as NBR (acrylonitrile butadiene rubber). In this connection, reference numeral 7 in FIG. 37 is a grease nipple.
A second conventional example of the linear guide apparatus is disclosed in Unexamined Japanese Patent Publication No. Hei. 6-346919 previously proposed by the present applicant. A third conventional example of the linear guide apparatus is disclosed in Unexamined Japanese Patent Publication No. Hei. 7-35146 previously proposed by the present applicant.
The second conventional example will be described as follows. Between the outer surface of the guide rail and the inner surface of the slider moving along the guide rail, there is provided a seal device having a seal lip portion made of rubber or synthetic resin containing lubricant. The seal lip portion comes into contact with an outer surface of the guide rail and seals a gap formed between the inner surface of the slider and the outer surface of the guide rail. Since the seal lip portion of the seal device is made of rubber or synthetic resin containing lubricant so that the seal lip portion has a self-lubricating property, the lubricant contained in the seal gradually oozes out and is automatically fed to a frictional surface of the seal portion. Therefore, the abrasion of the seal lip portion can be suppressed.
The third conventional example will be described as follows. At least a portion of the layer made of rubber or synthetic resin and a portion of the layer made of rubber or synthetic resin containing lubricant are overlapped and integrally joined. At least, on the layer of rubber or synthetic resin containing lubricant, there is formed a seal lip portion which comes into contact with an outer surface of the guide rail so as to seal a gap formed between the inner surface of the slider and the outer surface of the guide rail. Since the seal lip portion also has a self-lubricating property in this third conventional example, lubricant contained in the seal itself gradually oozes out and is fed to a frictional surface of the seal, so that the abrasion of the lip portion can be suppressed. Since the layers are overlapped as described above in the third conventional example, it is possible to provide the following advantages. When the number and thickness of the overlapped layers are appropriately determined, the mechanical strength of the seal lip portion can be arbitrarily set in accordance with the use of the linear guide apparatus.
As shown in FIGS. 52 to 53B, the sealing device of the second conventional example is described as follows. Lubricant is made to ooze from a surface of the guide rail 1 by the action of contact resistance of the seal 5. Accordingly, there is provided no relief 73 as shown in FIG. 53A in the contact portion 71 shown in FIG. 53B where the seal 5 comes into contact with the guide rail 1, but an area of the portion where the seal 5 comes into contact with the guide rail 1 is increased. Further, there is formed a recessed groove 72 in the contact portion 71 where the seal 5 comes into contact with the guide rail 1, so that the portion 71 is divided into two portions. Then the thus divided portions are contacted with the guide rail 1 by two steps. Therefore, the intrusion of foreign objects can be prevented by the contact of two steps better than the contact of one step. Further, lubricant can be held by the recessed groove 72, so that the sliding property of the seal 5 can be enhanced.
However, the above conventional linear guide apparatus has the following disadvantages.
As the slider 2 runs along the guide rail 1, a quantity of grease previously charged inside the slider 2 is decreased. Therefore, the lubrication between the lip portion of the side seal 5 and the guide rail 1 becomes poor, and also the lubrication between the lip portion of the under seal 6 and the guide rail 1 becomes poor. Due to the poor lubrication, the lip portions gradually wears away. Due to the progress of abrasion, the sealing property is deteriorated, and foreign objects such as cutting chips enter the inside of the slider 2, which shortens the life of the linear guide apparatus in some cases.
When the slider 2 runs and the rolling elements roll, grease can be fed to the rolling element rolling groove 3 of the guide rail 1 via the rolling elements. Accordingly, the abrasion is relatively small in a portion of the lip which comes into contact with the rolling element rolling groove 3. On the other hand, the abrasion tends to increase in a portion of the lip which comes into contact with an upper surface of the rail to which no grease is fed because of poor lubrication. Due to the foregoing, the lip portion wears away and damaged. In this way, the life of the linear guide apparatus is shortened.
From this point of view, when the above second example and the third one are adopted, the abrasion of the seal lip portion can be suppressed since the seal lip portion has a self-lubricating property. However, even in the above conventional examples, the following problems may be encountered. A quantity of lubricant oozing from rubber or synthetic resin containing lubricant is not sufficient to lubricate the balls and rollers which guide the movement of the slider of the linear guide apparatus, that is, it is difficult to maintain smooth rolling motions of the rolling elements such as balls and rollers.
In the sealing device containing lubricant of the above second conventional example or the third one, the seal lip portion is pressed against the guide rail only by the elasticity of the seal itself. Accordingly, it is possible to provide a sufficiently high pressing force as a seal, however, it is impossible to provide a sufficiently high pressing force as a lubricant feed unit.
Further, a shape of each portion of the guide rail 1 with which the seal 11 comes into contact, for example, a shape of the ball rolling groove, the guide rail side surface or the upper surface of the guide rail is complicated, and further the seal 11 is attached being a little displaced. Therefore, it is difficult for the seal 11 to be positively contacted with each portion of the guide rail 1. Accordingly, a sufficient quantity of lubricant can not be provided and the dust protecting property is deteriorated. As a result, the lubricant in the slider 2 is widely diffused.
The present invention has been accomplished to solve problems caused in a conventional linear guide apparatus. An object of the present invention is to provide a linear guide apparatus in which the abrasion of a sealing device is reduced by directly feeding lubricant to the lip portion or by feeding lubricant via the guide rail, so that a high sealing property can be maintained in the linear guide apparatus over a long period of time.
Another object of the present invention is to provide a linear guide apparatus in which lubricant can be fed at all times so as to maintain a smooth rolling motion of the rolling elements.
Still another object of the present invention is to provide a linear guide sealing device in which the seal can be positively contacted with each portion while the seal precisely follows the shape of each portion.
The objects of the invention are achieved by a linear guide apparatus which includes: an axially extending guide rail having a first rolling groove on its outer surface; a slider engaged with the guide rail and having a second rolling groove, rolling element return grooves and curved grooves, the second rolling groove confronting the first rolling groove, the rolling element return grooves being coupled to both end portions of the second rolling groove through the curved grooves, respectively; a plurality of rolling elements loaded into the slider to be made circulatable through the second rolling groove, the curved grooves, and the rolling element return grooves; and a sealing device fixed to the slider in slidable contact with the guide rail for sealing a clearance existing between the guide rail and the slider, the sealing device comprising: a lubricant-containing polymer member formed of a synthetic resin containing a lubricant, and having a contact portion contacting with the guide rail to surround the guide rail, both wing portions, a connecting portion connecting the wing portions to be C-shaped substantially, and a first plate member fitted to the lubricant-containing polymer member in which the lubricant-containing polymer member is interposed between the slider and the first plate member.
According to the invention, since a lubricant-containing polymer member is arranged close to the lip portion of a side seal which is provided in the sealing device, lubricant that has gradually oozed from the lubricant-containing polymer member is easily fed to the lip portion, so that the lip portion can be stably lubricated over a long period of time.
In addition, since at least a portion of the inner circumferential surface of the lubricant-containing polymer member comes into contact with the outer circumferential surface of the guide rail, the lip portion can be fed with lubricant via the guide rail. Therefore, it is possible to feed lubricant to the lip portion very stably. Accordingly, the abrasion of the lip portion can be minimized, and the sealing property of the sealing device can be maintained to be high over a long period of time.
Lubricant that has oozed from the lubricant-containing polymer member is also fed to the rolling elements via the guide rail. Accordingly, even when grease is exhausted from the apparatus for some reasons, the lubricant that has oozed out from the lubricant-containing polymer member functions as a lubricant of the linear guide apparatus itself.
Especially when the lubricant-containing polymer member is interposed between the slider end face and the side seal, the leakage of grease from the device can be reduced. The reason is described as follows. Conventionally, the lip portion of the sealing device gets rolled up during a normal reciprocating motion of the slider. At this time, grease leaks out from the device. On the other hand, according to the invention, the lubricant-containing polymer member is interposed between the slider end face and the side seal. Therefore, the lip portion is difficult to get rolled up, and the leakage of grease from the device can be reduced. In the case where the side seal is composed of a polyurethane rubber member containing grease which works as lubricant, the abrasion of the lip portion of the sealing device can be further reduced.
Further, according to the invention, when lubricant oozes from the lubricant-containing member which strides the guide rail, the lubricant-containing member shrinks by itself, so that a distance between both wing portions of the lubricant-containing member, which is arranged in a C-shape, is reduced, and further the inside faces of both wing portions of the lubricant-containing member, that is, the faces opposed to the side faces of the guide rail, are pushed against the guide rail. Therefore, the lubricant-containing member comes into contact with the guide rail at all times. Due to the pushing force generated by the pushing means, no gap is formed between the guide rail and the lubricant-containing member irrespective of errors caused in the manufacturing process. Therefore, the lubricant oozing from the lubricant-containing member can be stably fed to the guide rail. Particularly, the shape of the bottom surface of the C-shaped lubricant-containing member is formed into a predetermined shape of an arc. Therefore, even when the lubricant-containing member is deformed by the pushing force of the pushing means so that both wing portions are pressed against the guide rail, the shape of the arc on the bottom surface is put into a horizontal condition. Consequently, the lubricant-containing member stably comes into contact with the guide rail.
Moreover, according to the invention, a plurality of cutout portions are formed in a portion of the seal lip which comes into pressure contact with an outer surface of the guide rail. Therefore, the seal lip in which a plurality of cutout portions are formed can be contacted with the outer surface of the guide rail, the shape of which is complicated. In this way, the seal lip can easily follow the shape of the guide rail. Even when the lubricant feed device is dislocated in the assembling process, the seal lip having the cutout portions is deformed, so that the dislocation can be absorbed, and no gap is formed between the seal lip portion and the guide rail.
When a plurality of cutout portions are formed in the seal lip portion, the contact area of the seal lip portion with the guide rail can be increased, so that a quantity of lubricant oozing from the seal lip portion can be increased. When the seal lip portion is provided with a plurality of cutout portions, a space in which the lubricant is held can be increased as compared with a conventional arrangement. Therefore, the sliding property of the seal lip portion can be enhanced. Further, the number of the seal lip portions is increased as compared with a conventional arrangement, so that the intrusion of dirt and dust from the outside can be prevented, and the lubricant can be prevented from diffusing to the outside.